氨基苷类高水平耐药肠球菌的耐药性及修饰酶基因分布

The resistance and aminoglycoside-modifying enzyme genotypes of high-level amino-glycoside resistant Enterococcus

目的明确临床分离的氨基苷类高水平耐药肠球菌(HLAR)耐药性及修饰酶基因类型。方法用琼脂筛选法筛选出HLAR、庆大霉素高水平耐药肠球菌(HLGR)及链霉素高水平耐药肠球菌(HLSR);采用K-B法测定粪肠球菌及屎肠球菌对12种抗菌药物的耐药性;PCR及序列分析法检测7种氨基苷类修饰酶基因。结果肠球菌中HLAR为73.6%。利奈唑胺、万古霉素和替考拉宁对HLAR的抗菌作用最好,未检出耐药株。屎肠球菌中β内酰胺类抗生素耐药株以及喹诺酮类药物耐药株明显高于粪肠球菌。所有的屎肠球菌氨基苷类高耐株对氨苄西林、氨苄西林-舒巴坦及环丙沙星均耐药。aac(6')-Ie-aph(2")-Ia基因是HLGR的主要耐药基因,占HLGR的92.6%;3株HLGR存在与aph(2")-Id高同源性的基因。而6-'ant、3"-ant及str基因在HLSR中的检出率低。结论HLAR已成为医院感染的重要耐药菌。HLGR主要通过aac(6')-Ie-aph(2")-Ia基因编码的修饰酶造成对庆大霉素高度耐药。

Objective To determine the antibiotic resistance and aminoglycoside-modifying enzyme genotypes of high-level aminoglycoside resistant Enterococcus strains isolated from clinical specimens. Methods The high-level aminoglycoside resistant （ HLAR）, high-level gentamicin resistant （HLGR） and high-level streptomycin resistant （HLSR） isolates were screened by the agar screening method. The resistance of these strains to 12 antimicrobial agents was determined by K-B method. The aminoglycoside-modifying enzyme genes were detected by polymerase chain reaction （PCR）. Results The prevalence of HLAR was 73.60/00 in Enterococcus isolates. None of these HLAR isolates was found resistant to linezolid, vancomycin or teicoplanin. The prevalence of resistance to β-lactam antibiotics or quinolones was higher in Enterococcus faecium than in Enterococcus faecalis. The positive rate of aac（6′）-Ie-aph（2″）-Ia was 92.6% among HLGR isolates. Three HLGR isolates have the resistance gene mostly similar to aph（2″）-Id. The rates of 6′-ant, 3″-ant and str were all lower in HLSR strains. Conclusions HLAR Enterococcus spp. has become one of the most important antibiotic resistant pathogens of nosocomial infections. The resistance of HLGR is mainly conferred by aminoglycoside-modifying enzymes encoded by aac（6′）-Ie-aph （2″）-Ia.